The objective of the proposed research is to develop an understanding of the structure and physicochemical characteristics of molecules which influence the probability that the molecules will undergo bioactivation by mammalian arylhydroxamic acid acyltransferase (s). The objective will be accomplished by quantitatively evaluating the influence of substituents of varying chemical and physical properties upon the ability of arylhydroxamic acids to function as acyl donors in the acyltransferase reaction in vitro; substituted N-hydroxy-2-acetylaminofluorenes (N-hydroxy-2-fluorenylacetamides) and substituted N-hydroxy-trans-4-acetylaminostilbenes (N-hydroxy-trans-4-stilbenylacetamides) will be used as model substrates. Partially purified hepatic arylhydroxamic acid acyltransferase from rats will be used in these studies and enzyme activity will be monitored by spectrophotometric measurement of acyl group transfer to p-phenylazoaniline (4-aminoazobenzene) and by the use of N-acetylmethionine as a trapping agent for the activated intermediates. Data derived from this research may be expected to yield insights into the factors that influence the acyltransferase reaction and may also lead to methods to predict and, consequently, reduce the hazard associated with exposure to potentially carcinogenic or toxic arylamides and arylhydroxamic acids.